This invention relates to a novel liquid level detector for detecting the presence or absence of a liquid in a container, and more specifically relates to a novel ultrasonic circuit which includes an ultrasonic transducer which can be pressed against the outer wall of a liquid container such as a tank or pipe and which will produce an output signal which indicates whether there is a liquid in the container at the transducer location.
It is frequently desirable to determine whether a pipe or container is filled with a liquid or to determine the height of a liquid within a container. This is commonly done by gauges or other equipment which must penetrate the container wall and reach into the interior of the pipe or container. These gauges are then used to produce an indication of liquid level or the presence of liquid in the container, and can be used to operate liquid flow or liquid level controls. The need to gain access to the container interior has the obvious drawbacks of requiring special container designs and, in some cases, special seals to bring out gauge components, electrical wires, and the like. Moreover, these parts become subject to failure when exposed to corrosive fluids and hostile environments within a liquid container.